chore:Singleton

example/main.ts

 import { WebsocketError, WebSocketResp } from '../src/types';
 
 const url = 'ws://127.0.0.1:8081';
-const client = new Client(url, {
+const client = Client.getInstance(url, {
   onOpen(): void {
     client
       .ping({})

src/index.ts

 class Client {
   private _maxPayload: number;
   private _enableLogger: boolean;
+  private static instance: Client;
   private listeners: Map<number, (data: WebSocketResp) => void>;
   private requestHeader: string;
   private responseHeader: string;
    * @param url websocket链接地址
    * @param readyStateCallback 链接状态回调，可以处理onOpen、onClose、onError
    */
-  public constructor(url: string, readyStateCallback: ReadyStateCallback) {
+  private constructor(url: string, readyStateCallback: ReadyStateCallback) {
     this.listeners = new Map<number, (data: WebSocketResp) => void>();
     this.requestHeader = '';
     this.requestHeader = '';
     this.socket = this.connect();
   }
 
+  /**
+   * 通过单例模式获取客户端链接
+   * @param url websocket链接地址
+   * @param readyStateCallback 链接状态回调，可以处理onOpen、onClose、onError
+   */
+  public static getInstance(url: string, callback: ReadyStateCallback): Client {
+    if (!Client.instance) {
+      Client.instance = new Client(url, callback);
+    }
+
+    return Client.instance;
+  }
+
   /**
    * 设置可以处理的数据包上限
    * @param maxPayload 最多可以处理的数据包大小
   }
 }
 
-let client: Client;
-
-function getClient(url: string, callback: ReadyStateCallback): Client {
-  if (!client) {
-    client = new Client(url, callback);
-  }
-
-  return client;
-}
-
-export { Client, getClient };
+export { Client };